Vertical Boiler Project  5/7/11

Warning!!! The following articles are NOT plans for building a model boiler. There are no drawings or engineered specifications posted on these pages for a reason. These articles only serve as a record of my experience in building a vertical boiler. Please DO NOT try to use these articles as a guide to build you own boiler. They simply aren’t written for that purpose. Thank you...

Posted on May 7, 2011

       Hey folks!! I’m back at it and this time I am going to build a firebox and burner assembly for my new boiler. But before I work on that I need to tie up a loose end and set up my safety valves. Last week I tested my boiler with a live steam test in which I had reset one of my safety valves to blow off at 125 PSI. This valve will need to be reset to the working pressure of this boiler as well as add the second “reserve” safety valve to the opposite side boiler fitting.
       To do this I filled the boiler up to the top with water to eliminate excess compressed air in the vessel and then slowly charged the boiler to a 105 PSI with a regulator. I then set my #2 safety valve (to the right below) to blow off at 105 PSI
*** and then locked down the jamb nut. I also set my #1 safety valve (to the left below) to blow off at 100 PSI*** (water spray everywhere :0P). Note: Having the valves operate in a sequence will reduce the pressure in the boiler more gradually than if both of them blow off the same time.
       Now that I have that out of the way I can go right into my burner assembly.......
***Note: I have since reduced the normal working pressure of my boiler from 80 PSI to 60 PSI (75 PSI max pressure in lieu of 100 PSI originally) as to not stress the soft solder on the boiler fittings. I have set the blow off valves at 75 and 80 PSI respectively to allow for a 20% operating headspace. Keeping this type of silver bearing solder under 310° F will ensure that it will keep its strength at pressure...

       For a while now I have been debating on how to fire this boiler. I had originally envisioned using steam coal for my fuel as I really love the smell of a good coal fire. However there are a lot of drawbacks and inconveniences with burning coal that I am not too keen about.
       I can only see myself using this boiler frequently if it is simple to use and readily able to make steam. That is why I am choosing my fuel wisely. Most gaseous and liquid fuels are easy to use and are ready to fire immediately with little or no waste. These include Propane, Butane, Alcohol (Methanol, Ethanol and Isopropyl), Kerosene and White Gas (Coleman Fuel) to name a few.
       I have been weighing the availability and cost effectiveness of these fuels and have narrowed down my search to Propane and Coleman Fuel. I really like the smell of a Coleman stove (reminds me of camping) so I am going to choose Coleman fuel :0) Luckily for me Coleman fuel (white gas) is readily available, has a good shelf life (5 to 7 years) and is economical ($9 per gallon). The best part is that I can easily “modify” a Coleman camping burner to work with my boiler.

       I have decided to use a Coleman “Dual Fuel” 533 camping burner for my boiler project. This $47 burner is capable of producing around 10,000 BTUs per hour which should be more heat than I will need However the stove must be modified to work with my setup. Now it goes without saying that The Coleman Company does not want anyone messing with their burners as Coleman fuel is highly flammable. This is why I must mention the following:
      
Please do not attempt to modify any camping stove unless you are well versed in pressurized fuel systems. I will be purposely leaving out steps for this process as I cannot assume any responsibility for anyone getting hurt by trying this themselves. If one were to have the proper know-how to safely modify a burner then more power to them!!! Otherwise, DON’T DO IT!!!!!

       Coleman stoves use an evaporation system where the flames “boil” the incoming liquid fuel supply and turn it into a gaseous state. This is done with a “generator” or evaporator tube which is situated over the burner (brass tube seen above/below). Once the fuel is in a gaseous state it can be mixed with air and burned in the burner below the generator tube.
       The flow of gas is metered with a coaxial metering wire (not shown) which is situated inside the generator tube. This wire is moved into and pulled back out of the metering orifice by the adjustment lever (red handle above). This assembly is delicate and must be handled with care....

       The Coleman burner uses pressurized fuel which is forced into the generator tube for operation. The fuel is pressurized by a hand pump that introduces air pressure inside of the fuel tank and thus raises the fuel up to around 30 PSI. Because the fuel is under pressure it is important that no leaks occur during operation or else a major fire could result.
       Note : I think that it is worth mentioning that any gaseous or liquid fuel has it’s own inherent risk and should also be respected  just as highly.....

       In order to make this burner work with my boiler I will need to remove the burner assembly from the fuel tank so it can be remotely mounted into the boiler’s new firebox. This particular stove will take a little work to modify however there are other Propane models and camping fuel models that already have remote burners (separate tank and burner) that could be considered as alternatives to this design FYI.
       To modify my stove I disassembled the fittings and straightened out one end of the generator tube (seen above). The newly straightened out side of the tube will be where it will exit the firebox of the boiler. The next step was to tap out some 1/8” NPT threads into the flame adjustment lever (below left) to accommodate standard NPT pipe fittings. This will allow me to use 1/8” copper tube to extend the fuel line to the burner later on. Note: You will notice that I removed the original external threads from the metering lever....
       The next step was to make a siphon tube adaptor bushing (bottom right) to fit the tank side of the burner assembly that will support the original siphon tube. The bushing’s outer threads were cut at 32 TPI and the “inner inside” was cut at 40 TPI for the siphon tube (with a lathe). The “outer inside” was tapped out for 1/8” NPT just like the metering lever was earlier.

       The fuel valve that releases the fuel from the pressurized tank is now removed from the siphon tube (below - lower right) as it cannot be used with this type of configuration. Because of this I will need to add a fuel shut off valve to use the burner remotely....

       The tank siphon tube is screwed into the adaptor bushing as seen below.

       And now the bushing is screwed into the fuel tank. Thread sealant was used on this fitting (not shown).

       I was now able to add a 1/8” NPT to 1/8” copper tube adaptor valve to the tank for a positive fuel shut off point. I then plumbed the fuel line with 1/8”: copper tube for a burner test as seen below. I carefully filled up the tank and then pressurized the fuel for a burner test.
       I fired up the burner and checked for any abnormalities. Lucky for me it worked just like it did when the burner was on top of the tank :0) I ran the burner through the entire tank of fuel to make sure everything worked properly....

       Now that I have got my burner system out of the way I can build my firebox for the boiler. This will be made out of 304 stainless steel pipe as it is durable and resists corrosion unlike mild steel. The only drawback is that a stainless fire box will look somewhat out of place being married to this vintage looking boiler :0/ For the most part I am more interested in a boiler that will last for many years so stainless it is!!!
       I started out with a short piece of 6” 304 stainless steel pipe. I carefully cut the pipe to a length of 4” for the new fire box shell.

       I wanted the copper boiler shell to fit into the new firebox shell so that I can easily secure the boiler with four 10-24 brass screws. I needed to section in a piece of pipe to expand the diameter of the firebox pipe as seen below. This is because the 6” pipe that I had on hand was a bit too small to fit around the 6” boiler shell. You will notice that I made the sectioned in piece wider than the actual gap caused by the expansion. This was done to minimize warping during the welding process by keeping the welding beads separated....

       And with a quick zap of the TIG torch the firebox is welded....

       I ground down the welds inside and out and then surface ground the outer surface for a nice brushed look (not shown).

       I welded in a 16 gauge stainless bottom plate on the firebox as seen below....

       A series of 8 - 5/8” breather holes were drilled into the bottom of the firebox. I also welded on some 1/4” x 1” steel tabs to the bottom of the boiler as well as a foundation ring that will support the copper shell. The bracket on the left (below) will support the burner’s metering valve.....

       I drilled and tapped an 8-32 hole in the center bottom of the firebox. I then mounted the base bracket of the Coleman burner assembly as seen below....

       I now was able to test fit the generator tube.....

       And now the burner bowl was screwed into place. I used the breather holes to access the screw locations...

       Last but not least the burner ring set was secured in place. You will notice the fire door I made for the side of the firebox. This door will be used to light the fire as well as inspect the burner....

       I hooked up the 1/8” fuel line in preparation for a test run....

       Once again I fueled her up and ran the burner to check for any problems. Of course I did this with ample ventilation. I would not suggest doing this indoors however a carport or open garage seems reasonable. I kept a CO2 fire extinguisher on hand at all times....

       I screwed in the boiler shell for a final fit check....

       At this point I added a “blow down” valve to the bottom of the boiler. This valve is used to drain the boiler as well as blow out sediment and crud that may accumulate inside the boiler over time. I chose to use a ball type valve as it has the largest “clear bore” diameter to allow any solids to pass freely. However it is worth mentioning that a safety plug must be used with this type of valve as it would be easy to accidentally throw the valve and burn yourself (see the plug at the end of the down spout).
       It is also worth mentioning that you should not heat up a ball valve when closed as it can trap water inside the “ball” and create high pressure steam. I learned this lesson many years ago when sweating a ball valve on my house’s water main :oP The valve’s seal let loose and a ball of superheated steam hit me in the face :o( Needless to say I mounted this 1/4” NPT valve where it cannot get much hotter than 150° F.

       All that was left to do now was fire up the boiler to see if I could make steam in a reasonable amount of time. I filled the boiler up with distilled water and ignited the burner as the clock ticked on....

       At about the 8 minute mark I was up to about 60 PSI and climbing. Within two more minutes I was bordering 100 PSI so I let the safety valve cycle a couple of times to insure that it was working correctly. I then cracked open the main steam valve to purge some pressure which filled the garage with foggy steam. I was quite surprised at how well the burner was able to keep up the pressure considering the steam I was releasing....

       I now just have to build a smoke stack for the boiler and it is basically complete. I can’t wait to see if this thing will turn over my 6CI engine or better yet, produce some actual power!!!

       Please join me again for the next episode and until then remain inquisitive my friends!!!

Don R. Giandomenico

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